Why has this not been done before?

I ask this question often in client briefing meetings. "Your approach seems obvious, why did it take humanity as 2017 to come up with this, why is it so hard to do?" It is a useful question to take the position of the outsider. For the expert/insider the answer is so obvious that it does not even have to be included in the slides. For the outsider, it might be the most important piece of information.